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137 lines
3.6 KiB
C
137 lines
3.6 KiB
C
/***********************************************************
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Copyright 1991 by Stichting Mathematisch Centrum, Amsterdam, The
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Netherlands.
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All Rights Reserved
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Permission to use, copy, modify, and distribute this software and its
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documentation for any purpose and without fee is hereby granted,
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provided that the above copyright notice appear in all copies and that
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both that copyright notice and this permission notice appear in
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supporting documentation, and that the names of Stichting Mathematisch
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Centrum or CWI not be used in advertising or publicity pertaining to
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distribution of the software without specific, written prior permission.
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STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
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THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
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FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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******************************************************************/
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/* Parser accelerator module */
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/* The parser as originally conceived had disappointing performance.
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This module does some precomputation that speeds up the selection
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of a DFA based upon a token, turning a search through an array
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into a simple indexing operation. The parser now cannot work
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without the accelerators installed. Note that the accelerators
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are installed dynamically when the parser is initialized, they
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are not part of the static data structure written on graminit.[ch]
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by the parser generator. */
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#include "pgenheaders.h"
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#include "grammar.h"
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#include "token.h"
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#include "parser.h"
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/* Forward references */
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static void fixdfa PROTO((grammar *, dfa *));
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static void fixstate PROTO((grammar *, dfa *, state *));
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void
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addaccelerators(g)
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grammar *g;
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{
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dfa *d;
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int i;
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#ifdef DEBUG
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printf("Adding parser accellerators ...\n");
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#endif
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d = g->g_dfa;
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for (i = g->g_ndfas; --i >= 0; d++)
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fixdfa(g, d);
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g->g_accel = 1;
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#ifdef DEBUG
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printf("Done.\n");
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#endif
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}
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static void
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fixdfa(g, d)
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grammar *g;
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dfa *d;
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{
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state *s;
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int j;
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s = d->d_state;
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for (j = 0; j < d->d_nstates; j++, s++)
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fixstate(g, d, s);
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}
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static void
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fixstate(g, d, s)
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grammar *g;
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dfa *d;
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state *s;
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{
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arc *a;
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int k;
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int *accel;
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int nl = g->g_ll.ll_nlabels;
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s->s_accept = 0;
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accel = NEW(int, nl);
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for (k = 0; k < nl; k++)
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accel[k] = -1;
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a = s->s_arc;
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for (k = s->s_narcs; --k >= 0; a++) {
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int lbl = a->a_lbl;
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label *l = &g->g_ll.ll_label[lbl];
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int type = l->lb_type;
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if (a->a_arrow >= (1 << 7)) {
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printf("XXX too many states!\n");
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continue;
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}
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if (ISNONTERMINAL(type)) {
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dfa *d1 = finddfa(g, type);
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int ibit;
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if (type - NT_OFFSET >= (1 << 7)) {
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printf("XXX too high nonterminal number!\n");
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continue;
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}
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for (ibit = 0; ibit < g->g_ll.ll_nlabels; ibit++) {
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if (testbit(d1->d_first, ibit)) {
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if (accel[ibit] != -1)
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printf("XXX ambiguity!\n");
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accel[ibit] = a->a_arrow | (1 << 7) |
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((type - NT_OFFSET) << 8);
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}
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}
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}
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else if (lbl == EMPTY)
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s->s_accept = 1;
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else if (lbl >= 0 && lbl < nl)
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accel[lbl] = a->a_arrow;
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}
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while (nl > 0 && accel[nl-1] == -1)
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nl--;
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for (k = 0; k < nl && accel[k] == -1;)
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k++;
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if (k < nl) {
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int i;
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s->s_accel = NEW(int, nl-k);
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if (s->s_accel == NULL) {
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fprintf(stderr, "no mem to add parser accelerators\n");
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exit(1);
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}
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s->s_lower = k;
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s->s_upper = nl;
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for (i = 0; k < nl; i++, k++)
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s->s_accel[i] = accel[k];
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}
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DEL(accel);
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}
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